Axel%20Drees,%20Stony%20Brook%20University

1
High T QCD at RHIC Hard Probes

• Fundamental open questions for high T QCD
• Nature of matter created at RHIC
• Critical Point
• Hadronization
• Rapid thermalization
• Experimental quest for answers
• Status of key experimental probes
• limitations of progress and solutions with
  upgrades of RHIC
• Ongoing and planed improvements to RHIC
• Time line, detector and accelerator upgrades
  (RHIC II)
• Summary

2
Exploring the Phase Diagram of QCD
Study high T and r QCD in the Laboratory

• Quark Matter Many new phases of matter
• Asymptotically free quarks gluons
• Strongly coupled plasma
• Superconductors, CFL .
• Experimental access to high T and moderate r
  region heavy ion collisions
• Pioneered at AGS and SPS
• Ongoing program at RHIC

T
Quark Matter
Mostly uncharted territory
sQGP
TC170 MeV
Hadron Resonance Gas
Overwhelming evidence Strongly coupled quark
matter produced at RHIC
temperature
Nuclear Matter
baryon chemical potential
940 MeV
1200-1700 MeV
mB
3
Quark Matter Produced at RHIC
III. Jet Quenching
I. Transverse Energy
Bjorken estimate t0 0.3 fm
PHENIX 130 GeV
dNg/dy 1100
central 2
? 10-20 GeV/fm3
II. Hydrodynamics
Initial conditions ?therm 0.6
-1.0 fm/c ?15-25 GeV/fm3
Heavy ion collisions provide the laboratory to
study high T QCD!
4
Fundamental Questions
and our experimental approach at RHIC

• Is the quark-gluon plasma the most perfect
  liquid? If not, what are its quasi particles?
• Hard penetrating probes with highest possible
  luminosity at top RHIC energies
• Excitation function and flavor dependence of
  collective behavior
• Is there a critical point in the QCD phase
  diagram and where is it located?
• Low energy scan of hadron production
• Low energy scan of dilepton production with
  highest possible luminosity
• How does the deconfined matter transform into
  hadrons?
• Flavor dependence of spectra and collective flow
• How are colliding nuclei converted into thermal
  quark-gluon plasma so rapidly?
• Hard probes at forward rapidity

Question formulated at QCD workshop, Washington
DC 12/2006
5
Fundamental Question (I)

• Is the quark-gluon plasma the most perfect
  liquid? If not, what are its quasi particles?
• What are the properties of new state of matter?
• Temperature, density, viscosity, speed of sound,
  diffusion coefficient, transport coefficients .
• If its a fluid What is the nature a
  relativistic quantum fluid?
• If not What is it and what are the relevant
  degrees of freedom?

Key are precision measurements with hard probes
and of collective behavior currently not
accessible at RHIC ? RHIC upgrades improved
detectors and increased luminosity
6
Key Experimental Probes of Quark Matter

• Rutherford experiment a ? atom discovery of
  nucleus
• SLAC electron scattering e ?
  proton discovery of quarks

QGP
penetrating beam (jets or heavy particles)
absorption or scattering pattern
Nature provides penetrating beams or hard
probes and the QGP in A-A collisions

• Penetrating beams created by parton scattering
  before QGP is formed
• High transverse momentum particles ? jets
• Heavy particles ? open and hidden charm or bottom
  
• Calibrated probes calculable in pQCD
• Probe QGP created in A-A collisions as transient
  state after 1 fm

7
Hard Probes Light quark/gluon jets

• Status
• Calibrated probe
• Strong medium effect
• Jet quenching
• Reaction of medium to probe (Mach cones,
  recombination, etc. )
• Matter is very opaque
• Significant surface bias
• Limited sensitivity to energy loss mechanism

Answers will come from jet tomography (g-jet)
single, two
and three particle analysis Progress limited
by statistics (pT reach) ? increase luminosity
and/or rate capability kinematic coverage ?
increase acceptance add pid
Which observables are sensitive to details of
energy loss mechanism? What is the energy loss
mechanism? Do we understand relation between
energy loss and energy density? What phenomena
relate to reaction of media to probe?
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Jet Tomography at RHIC II
Medium reacting hadron lt 5 GeV
W.Vogelsang NLO RHIC II L 20nb-1 LHC 1
month run

• or p0
• trigger

without RHIC II
ltzgt 0.1 for particles in recoil jet
with RHIC II

• RHIC II luminosities will give jets up to 50 GeV
• separation of medium reaction and energy loss
• sufficient statistics for 3 particle
  correlations pT gt 5 GeV
• 2-3 particle correlations with identified
  particles

9
Hard Probes Open Heavy Flavor

• Status
• Calibrated probe?
• pQCD under predicts cross section by factor 2-5
• Factor 2 experimental differences in pp must be
  resolved
• Charm follows binary scaling
• Strong medium effects
• Significant charm suppression
• Significant charm v2
• Upper bound on viscosity ?
• Little room for bottom production
• Limited agreement with energy loss calculations

Electrons from c/b hadron decays
What is the energy loss mechanism? Where are the
B-mesons?
Answers expected from direct charm/beauty
measurements Progress limited by no b-c
separation ? decay vertex with silicon vertex
detectors statistics (B?J/?) ? increase
luminosity and/or rate capability
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Direct Observation of Charm and Beauty
m ct GeV mm D0
1865 125 D 1869 317 B0
5279 464 B 5279 496

• Detection options with vertex detectors
• Beauty and low pT charm through displaced e
  and/or m
• Beauty via displaced J/?
• High pT charm through D ? ? K

e
RHIC II increases statistics by factor gt10
11
Hard Probes Quarkonium

• Status
• J/y production is suppressed
• Similar at RHIC and SPS
• Consistent with consecutive melting of c and y
• Consistent with melting J/y followed by
  regeneration
• Recent Lattice QCD developments
• Quarkonium states do not melt at TC

RAA
Is the J/y screened or not? Can we really extract
screening length from data?
J/y
Answers require quarkconium spectroscopy
Progress limited by statistics (?, ?) ?
increase luminosity and/or rate capability
12
Quarkonium and Open Heavy Flavor
Compiled by T.Frawley
RHIC II 20 nb-1 LHC on
month
Signal h or h PHENIX lt0.35, 1.2-2.4 STAR lt1 ALICE lt0.9, 2.5-4 CMS lt2.4 ATLAS lt2.4
J/Y ? mm or ee 440,000 220,000 390,000 40,000 8K-100K
Y? mm or ee 8000 4000 7,000 700 140-1800
cc ? mmg or eeg 120,000 - - - -
?? mm or ee 1400 11000 6000 8000 15,000
B ? J/Y ? mm (ee) 8000 2500 12,900 - -
D ? Kp 8000 30,000 8,000 - -
LHC relative to RHIC Luminosity 10 Running
time 25 Cross section 10-50x similar
yields!
large background states maybe not
resolved min. bias trigger pt gt 3 GeV
Will be statistics limited at RHIC II (and LHC!)
13
Fundamental Questions (III)
? with TOF barrel

• How does the deconfined matter transform into
  hadrons?
• Status
• Elliptic flow (v2)
• v2 of mesons and baryons scale with constituent
  quark number
• Evidence for deconfined quarks
• Hadronisation via recombination of constituent
  quarks in QGP

STAR AuAu 62.4 GeV
Progress from ?s and flavor dependence of
collective flow Limited by flavor
detection capabilities s, c, b mesons and baryons
? vertex detectors and extended particle ID
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Fundamental Questions (IIII)

• How are colliding nuclei converted into thermal
  quark-gluon plasma so rapidly?
• Initial state and entropy generation.
• What is the low x cold nuclear matter phase?

• Status
• Intriguing hints for CGC
• (color glass condensate) at RHIC
• Bulk particle multiplicities
• mono jets at forward rapidity

STAR
Answers at RHIC from hard probes at forward
rapidity,
ultimately EIC needed Progress at RHIC limited
by detection capabilities ? forward
detector upgrades
15
Long Term Timeline of Heavy Ion Facilities
2012
2009
2015
2006
RHIC
Vertex tracking, large acceptance, rate
capabilities
PHENIX STAR upgrades
electron cooling RHIC II
electron injector/ring e RHIC
LHC
FAIR
Phase III Heavy ion physics
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RHIC Upgrades
On going effort with projects in different stages
Accelerator upgrades
Detector upgrades

• EBIS ion source
• Electron cooling (x10 luminosity) by 2008
• at 200 GeV extra x10
• AuAu 40 KHz event rate
• Electron cooling at lt20 GeV
• Additional factor of 10
• AuAu 20 GeV 15 KHz event rate
• AuAu 2 GeV 150 Hz event rate

Completed, on going, proposal submitted, in
preparation
17
Fundamental Questions
and our experimental approach at RHIC

• Is the quark-gluon plasma the most perfect
  liquid? If not, what are its quasi particles?
• Hard penetrating probes with highest possible
  luminosity at top RHIC energies
• Excitation function and flavor dependence of
  collective behavior
• Is there a critical point in the QCD phase
  diagram and where is it located?
• Low energy scan of hadron production
• Low energy scan of dilepton production with
  highest possible luminosity
• How does the deconfined matter transform into
  hadrons?
• Flavor dependence of spectra and collective flow
• How are colliding nuclei converted into thermal
  quark-gluon plasma so rapidly?
• Hard probes at forward rapidity

Key measurements and many precision measurements
unavailable at RHIC today! Progress
requires Improved detectors (STAR and
PHENIX) vertex tracking, large acceptance, rate
capability Luminosity upgrade (RHIC
II) electron cooling for all energies Improved
theoretical guidance phenomenological tools
(e.g. 3-D viscous hydro) lattice QCD (e.g.
finite density) new approaches (e.g.
gauge/gravity correspondence)
Question formulated at QCD workshop, Washington
DC 12/2006
18
Backup
19
Which Measurements are Unique at RHIC?

• General comparison to LHC
• LHC and RHIC (and FAIR) are complementary
• They address different regimes (CGC vs sQGP vs
  hadronic matter)
• Experimental issues Signals at RHIC
  overwhelmed by backgrounds at LHC
• Measurement specific (compared to LHC)
• Jet tomography measurements and capabilities
  complementary
• RHIC large calorimeter and tracking coverage
  with PID in few GeV range
• Extended pT range at LHC
• Charm measurements favorable at RHIC
• Abundant thermal production of charm at LHC, no
  longer a penetrating probe
• Large contribution from jet fragmentation and
  bottom decay
• Charm is a light quark at LHC
• Bottom may assume role of charm at LHC
• Quarkonium spectroscopy J/?, ? , ?c easier to
  interpreter at RHIC
• Large background from bottom decays and thermal
  production at LHC
• Rates about equal LHC 10-50 s, 10 luminosity,
  25 running timer
• Low mass dileptons challenging at LHC
• Huge irreducible background from charm production
  at LHC

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Beyond PHENIX and STAR upgrades?

• Do we need (a) new heavy ion experiment(s) at
  RHIC?
• Likely, if it makes sense to continue program
  beyond 2020
• Aged mostly 20 year old detectors
• Capabilities and room for upgrades exhausted
• Delivered luminosity leaves room for improvement
• Nature of new experiments unclear at this point!
• Specialized experiments or 4p multipurpose
  detector ???
• Key to future planning
• First results from RHIC upgrades
• Detailed jet tomography, jet-jet and g-jet
• Heavy flavor (c- and b-production)
• Quarkonium measurments (J/?, ? , ?)
• Electromagnetic radiation (ee- pair continuum)
• Status of low energy program
• Tests of models that describe RHIC data at LHC
• Validity of saturation picture
• Does ideal hydrodynamics really work
• Scaling of parton energy loss
• Color screening and recombination

New insights and short comings of RHIC detectors
will guide planning on time scale 2010-12
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Fundamental Questions (I II)

• Key probe electromagnetic radiation
• No strong final state interaction
• Carry information from time of emission to
  detectors
• g and dileptons sensitive to highest temperature
  of plasma
• Dileptons sensitive to medium modifications of
  mesons
• (only known potential handle on chiral symmetry
  restoration!)

• Status
• First indication of thermal radiation at RHIC
• Strong modification of meson properties
• Precision data from SPS, emerging data from RHIC
• Theoretical link to chiral symmetry restoration
  remains unclear

NA60
Can we measure the initial temperature? Is there
a quantitative link from dileptons to chiral
symmetry resoration?
Answers will come with more precision data ?
upgrades and low energy running
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RHIC II Accelerator upgrades
RHIC Heavy Ion Collisions

• EBIS ion source
• 30 higher e with UU
• Luminosity increase at 200 GeV
• x4 above design achieved by 2008
• Electron cooling at 200 GeV extra x10
• AuAu 40 KHz event rate
• Electron cooling at lt20GeV
• Additional factor of 10
• AuAu 20 GeV 15 KHz event rate
• AuAu 2 GeV 150 Hz event rate

Increase by additional factor 10 with electron
cooling
Expected whole vertex minbias event rate Hz
T. Roser, T. Satogata
23
Quarkonium and Open Heavy Flavor
Compiled by T.Frawley
Signal h or h PHENIX lt0.35, 1.2-2.4 STAR lt1 ALICE lt0.9, 2.5-4 CMS lt2.4 ATLAS lt2.4
J/Y ? mm or ee 440,000 220,000 390,000 40,000 8K-100K
Y? mm or ee 8000 4000 7,000 700 140-1800
cc ? mmg or eeg 120,000 - - - -
?? mm or ee 1400 11000 6000 8000 15,000
B ? J/Y ? mm (ee) 8000 2500 12,900 - -
D ? Kp 8000 30,000 8,000 - -
LHC relative to RHIC Luminosity 10 Running
time 25 Cross section 10-50x similar
yields!
Potential improvements with dedicated
experiment 4p acceptance J/Y, Y 10x ?
2-10x background rejection cc ????
Note for B, D increase by
factor 10 extends pT by 3-4 GeV
Will be statistics limited at RHIC II (and LHC!)
large background states maybe not
resolved min. bias trigger pt gt 3 GeV
24
Future PHENIX Acceptance for Hard Probes
EMCAL
0 f coverage 2p
EMCAL
-3 -2 -1
0 1 2
3 rapidity
(i) p0 and direct g with combination of all
electromagnetic calorimeters (ii) heavy flavor
with precision vertex tracking with silicon
detectors combine (i)(ii) for jet tomography
with g-jet (iii) low mass dilepton measurments
with HBD PHENIX central arms
25
RHIC Upgrades Overview
Upgrades High T QCD High T QCD High T QCD High T QCD Spin Spin Low x
  ee- heavy jet quarkonia W DG/G  
    flavor tomography        
PHENIX              
hadron blind detector (HBD) X            
Vertex tracker (VTX and FVTX) X X O O   O O
m trigger       O X    
forward calorimeter (NCC)     O X O   X
               
STAR              
time of flight (TOF)   O X O      
Heavy flavor tracker (HFT)   X O O      
tracking upgrade   O O    X O  
Forward calorimeter (FMS)           O X
DAQ   O X X O O O
               
RHIC luminosity O O X X O O O
X upgrade critical for success O upgrade
significantly enhancements program
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Comparison of Heavy Ion Facilities
Initial conditions

• FAIR cold but dense baryon
• rich matter
• fixed target p to U
• ?sNN 1-8 GeV UU
• Intensity 2 109/s ? 10 MHz
• 20 weeks/year
• RHIC dense quark matter to
• hot quark matter
• Collider pp, dA and AA
• ?sNN 5 200 GeV UU
• Luminosity 8 1027 /cm2s ? 50 kHz
• 15 weeks/year
• LHC hot quark matter
• Collider pp and AA
• Energy 5500 GeV PbPb
• Luminosity 1027 /cm2s ? 5 kHz
• 4 week/year

FAIR ? TC
LHC 3-4 TC
RHIC ? 2 TC
RHIC is unique and at sweet spot
Complementary programs with large overlap High
T LHC ? adds new high energy probes ? test
prediction based on RHIC data High r FAIR ?
adds probes with ultra low cross section
27
Midterm Strategy for RHIC Facility
Key measurements require upgrades of detectors
and/or RHIC luminosity

• Detectors
• Particle identification ? reaction of medium to
  eloss, recombination
• Displaced vertex detection ? open charm and
  bottom
• Increased rate and acceptance ? Jet tomography,
  quarkonium, heavy flavors
• Dalitz rejection ? ee- pair continuum
• Forward detectors ? low x, CGC
• Accelerator
• EBIS ? Systems up to UU
• Electron cooling ? increased luminosity

28
PHENIX Detector Upgrades at a Glance

• Central arms
• Electron and Photon measurements
• Electromagnetic calorimeter
• Precision momentum determination
• Hadron identification
• Muon arms
• Muon
• Identification
• Momentum determination

• Dalitz/conversion rejection (HBD)
• Precision vertex tracking (VTX)
• PID (k,p,p) to 10 GeV (Aerogel/TOF)
• High rate trigger (m trigger)
• Precision vertex tracking (FVTX)
• Electron and photon measurements
• Muon arm acceptance (NCC)
• Very forward (MPC)

29
STAR Upgrades
DAQ and TPC-FEE upgrade
Integrated Tracking Upgrade
Forward silicon tracker
HFT pixel detector
Barrel silicon tracker
30
Comments on High pT Capabilities
Region of interest for associated particles up
to pT 5 GeV

• LHC
• Orders of magnitude larger cross sections
• 3 times larger pT range
• RHIC with current detectors ( upgrades)
• Sufficient pT reach
• Sufficient PID for associated particles
• What is needed is integrated luminosity!